"The same chronological pattern points to a substantially shorter period of chronological and demographic overlap between the earliest ... modern humans and the last survivors of the preceding Neanderthal populations," the professor of prehistory and human evolution writes.

The reassessment is based on advances in eliminating modern carbon contamination from ancient bone fragments and recalibration of fluctuations in the pattern of the Earth's original carbon 14 content.

University researchers have, for example, found better ways of preparing bone collagen for analysis. This involves a process of ultrafiltration, which removes contaminants with a lower molecular weight, such as organic salts and humic acids.

And taking into account the carbon signature of deep-sea sediments and ice cores, has allowed researchers to recalibrate radiocarbon ages.

Taking over the world

Populations of anatomically and behaviourally modern humans first appeared in the Middle East some 45,000 years ago and slowly expanded into southeastern Europe.

Previously it was thought that this spread took place between 43,000 and 36,000 years ago.

But the re-evaluated data suggests that it actually happened between 46,000 and 41,000 years ago, starting earlier and moving faster.

"Evidently the native Neanderthal populations of Europe succumbed much more rapidly to competition from the expanding biologically and behaviourally modern populations than previous estimates have generally assumed," Mellars writes.

He says the invasion could have been helped by a major change in the climate that modern man would have been technologically and culturally better equipped to deal with than the more primitive Neanderthals.

"There are increasing indications that over many areas of Europe, the final demise of the Neanderthal populations may have coincided with the sudden onset of very much colder and drier climatic conditions," Mellars writes.

"This could have delivered the coup de grace to the Neanderthals in many parts of western and central Europe in their economic and demographic competition with the incoming modern groups," he adds.